The dyeing of textile webs is commonly achieved in one of two manners, one being immersing the textile web in a bath of dye solution so that the dye soaks into the textile web and the other being applying dye to (e.g., by spraying or coating) one or both faces of the textile web. Immersion (also commonly referred to as dip-coating) of the textile web requires a substantial amount of dye solution to be used to saturate the textile web. In addition, following saturation the textile web must be washed to remove a substantial amount of unbound dye from the web. While dip-coating results in good penetration of the dye throughout the entire textile web, it presents a relatively inefficient use of the dye solution and requires considerable post-processing of the web.
Dye may instead be applied to one or both faces of the textile web by any number of application techniques including, without limitation, ink jet systems, spray systems, gravure roll, slot die, rod coater, rotary screen curtain coater, air knife, brush and the like. Following the application of dye to the web, the web is often heated and/or steamed to promote binding of the dye to the textile web. The textile web may then be washed, such as in a bath of water or other cleaning solution, to remove unbound and excess dye from the web.
Applying dye to the textile web in this manner (e.g., as opposed to dip-coating) requires considerably less dye to be initially applied to the web, and thus reduces the time spent heating/steaming the web to facilitate binding of the dye to the web, and also reduces the amount of unbound dye that needs to be subsequently washed from the web. Such dyeing operations where the dye is applied to only one face of the textile generally use less dye, but run the associated risk that dye does not adequately penetrate into and through the web to the opposite face to provide even or uniform coloring of the web. While dyeing both faces of the textile web somewhat reduces this risk it also requires additional dye to be used, resulting in more unbound dye that must be subsequently removed from the web.
To this end, a co-pending U.S. application entitled PROCESS FOR DYEING A TEXTILE WEB, application Ser. No. 11/647,534 and filed Dec. 28, 2006, the entire disclosure of which is incorporated herein by reference, discloses a dyeing process in which dye is applied to only one face of a textile web and then the opposite face of the web is subjected to ultrasonic vibration to facilitate the migration of the dye into and through the web.
Once dye is applied to the web, it is also common to subject the dyed web to a drying process to bind the dye to the web. For solvent based dyes (e.g., comprising water or organic solvent), conventional drying is carried out by placing the dyed web in an oven at a suitable temperature to dry the dye to thereby facilitate binding of the dye to the web. Where webs are dyed in a continuous, or line feed process, such a drying process often takes a relatively considerable amount of time compared to the desired speed at which the web is to be moved.
There is a need, therefore, for a dyeing process that reduces the amount of dye that needs to be used in dyeing a textile web and facilitates improved penetration of the dye into and through the web during processing, as well as facilitating enhanced and/or expedited binding of the dye to the web. While the ultrasonic vibration used in the process described in the above-referenced co-pending application does generate heat and therefore facilitate some initial binding of the dye to the web (e.g., by evaporating some of the solvent), an enhanced or expedited process is advantageous.